The Collaborative International Dictionary of English v.0.48:

Alimentary \Al`i*men"ta*ry\, a. [L. alimentarius, fr. alimentum:
   cf. F. alimentaire.]
   Pertaining to aliment or food, or to the function of
   nutrition; nutritious; alimental; as, alimentary substances.
   [1913 Webster]

   Alimentary canal, the entire channel, extending from the
      mouth to the anus, by which aliments are conveyed through
      the body, and the useless parts ejected.
      [1913 Webster]

WordNet (r) 3.0 (2006):

alimentary canal
    n 1: tubular passage of mucous membrane and muscle extending
         about 8.3 meters from mouth to anus; functions in digestion
         and elimination [syn: alimentary canal, alimentary
         tract, digestive tube, digestive tract,
         gastrointestinal tract, GI tract]